Certain applications require pumps to be downhole to boost low borehole pressure so that the fluids produced can be brought to the surface. Some of these applications involve the need to heat the fluid to be produced so that it will flow into the wellbore. Steam assisted gravity drain systems (SAGD) typically heat the formation in a range of about 180 to 300° C. or higher in an injector well that gets the oil less viscous so that it can flow by gravity into an adjacent well below. A pump is located in the well below to bring the oil to the surfaces. Typically these submersible pumps have been driven by an electric motor with a power cable run down to it in the producing well. Electric motors have temperature service limits and operating temperatures in the production well in SAGD systems have gotten high enough as to meet or exceed the service limits of components in electric motors.
Accordingly, there was a need to provide a driver to a downhole motor that can operate at the temperature conditions in such SAGD wells and still produce the required horsepower in a confined wellbore location where space is at a premium. Various pumps in the past have been shown in patents being driven by non-electric motors. Some examples are U.S. Pat. Nos. 2,726,606; 6,234,770; 4,201,060; 4,576,006; US Publication 2005/0011649 and U.S. Pat. No. 5,823,261.
In one case single or stacked stages of steam driven fans are provided on a supply and return headers to drive a downhole pump to bring up well fluids. This reference is U.S. Pat. No. 7,566,208. This reference illustrates certain limitations of the prior art particularly in SAGD application. The illustrated “fans” in this reference will not be able to generate enough power to pump viscous fluids. The running of discrete supply and return headers for the motive fluid, even if it is steam, will not be feasible in many installations due to a simple lack of space.
What is needed is an arrangement that generates the requisite power in the space available and still brings up the produced fluid to the surface. In an SAGD application, the motive fluid keeps the produced fluid warm so that the energy required to bring it to the surface is controlled. Using a unique well configuration system more space is allocated for motive fluid supply and return using a U-shaped well for produced fluid collection and an injector well disposed adjacent and above the U-shaped well. A shroud assembly separates the produced fluid intake from the exhausted motive fluid preferable to the point where the producing well goes vertical so that the path of least resistance for the exhaust motive gasses is uphole. This minimizes the mixing of the produced fluid with the motive fluid. Those skilled in the art will better appreciate more aspects of the invention from a review of the detailed description of the preferred embodiment and the associated drawings while appreciating that the full scope of the invention is determined by the appended claims.